What were the top predators in North and South America?

Back in the old-timey days when *South America and North America were still islands. I think the predators that we think of today (cats, dogs, bears, etc.) came over courtesy of the land bridge with Asia. If I’m wrong, please set me straight. If not, what savage animal was at the top of the food chain on those respective (and very big) islands.

*After SA had separated from Africa, and NA had separated from “Europe” and had not yet “connected” with eastern “Asia.”

The top predador when humans first occupied North America was undoubtedly the saber-toothed cat.

The Panamanian Gap was finally bridged around 3.5 million years ago. Up until that time, “true” carnivores didn’t exist in South America, according to this page:

In North America, it could well have been ancestors of the sabretooth cats which were supreme before the gap closed.

Before the panama land bridge formed, South America had a completely different set of animals. South America had been an island continent since the extinction of the dinosaurs. There were marsupials (like the oppossum), xenarthrans (armadillos, sloths, and anteaters), rodents (many giants, like the capybaras, porcupines, guinea pigs, etc.), monkeys, and many species of notungulates…South American ungulates completely unrelated to artiodactyls or perrisodactyls and coming in all shapes and sizes.

Probably the largest predator was Thylacosmilus, a gigantic marsupial with huge sabre teeth, convergent with the placental Smilodon of North America although of course completely unrelated. If you are interested in South American mammal evolution, GG Simpson’s book “Splendid Isolation” is a great place to start.

North America also had some nasty crocodilians.

Not sure about S.A. (?)

Also, let us not forget the anaconda in S.A.

I’d suspect that the terror birds were close to the top in SA, also.

However. . .

That still leaves the question about NA, before the cats arrived. I don’t think they were native to North America, but immigrants from Asia.

The trouble is that NA was never as isolated as SA. Immigrants from Asia and Europe arrived every so often depending on sea levels.

OK, but you are interested in pre-cat times, so we just have to figure out the first recorded cats in NA, and find out some large NA predators from that time. I’ll have to wait till I get home…

The borhyaenids, a group of marsupial carnivores, were the dominant quadrupedal South American predators during the later Tertiary. I presume the sparassodonts are more or less synonynous with them (either a direct synonym or one being a subset of the other).

During Paleocene and Eocene times, South America had perhaps the last major archosaur land predators – the sebecosuchids, long-legged, deep-and-narrow-headed crocodiles adapted for land carnivory. Later the dominant predators were phorusrhacids, giant crane-like birds that held even the borhyaenids at bay and were quite capable of taking down a litoptern.

AFAIK North American Tertiary carnivores were variations on the standard issue – canoids and feloids, along with raptors (the birds, not the dinosaurs).

OK, I think I have some contenders for North American predators: Patriofelis and Mesonyx.

Source: “Thread of Life” by Roger Lewin

You’re all forgetting about the age of the terror birds when they ruled south america for millions of years as the top predator.


“You’re all forgetting about the age of the terror birds when they ruled south america for millions of years as the top predator.”

Except Earl Snake-Hips Tucker :o

Astro, it was I (it was me?) who beat you to the Phorusrhacids – though you did a beautiful job on it, with cites!

Unless you mean that they were the top South American predator except for Earl! :slight_smile: (Those snake-hips probably come in handy when chasing down prey! :D)

For North America, it all depends on what point in the Tertiary you’re talking about. There were a lot of different creodonts and carnivores across the 64 million years of the Tertiary Period. While within its limited niche Smilodon was probably the top predator, the American lion (a distinct subspecies of good old Panthera leo) and the dire wolf (Canus dirus), a pack-hunting animal about the size of a tiger (but taller, because longer legs), would also be important predators, and probably the more common.